My 10 year old male bun has PTSD, he's always been aggressive to people & other rabbits. For 6 years he lived alone next to another rabbit. Then we tried bonding but he rejected all of them. When he was 8 I adopted a pair of year old girls.. took a week to bond & they've all been happy ever since. He's growley & lunges at people still, but the biting stopped. He's not so sensitive to touch now so I can stroke his bum when he faces away & he's ok with it. He even licked me once, I cried

Aaaanyways, moral of the story is it's never too late & it can work out. I totally get why you'd rehome him as your priority has to be 'your own' rabbits but you're also going to struggle to find someone to take him I'm guessing. I don't know what to suggest but maybe Gwen at Bunny Burrows can help (maybe even take him, I don't know)